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High capacitance density three-dimensional (3D) metal-insulator-semiconductor (MIS) capacitors using Si nanowires (SiNWs) by metal-assisted chemical etching and atomic-layer-deposited alumina dielectric film were fabricated and electrically characterized. A chemical treatment was used to remove structural defects from the nanowire surface, in order to reduce the density of interface traps at the Al2O3/SiNW interface. SiNWs with two different lengths, namely, 1.3 μm and 2.4 μm, were studied. A four-fold capacitance density increase compared to a planar reference capacitor was achieved with the 1.3 μm SiNWs. In the case of the 2.4 μm SiNWs this increase was ×7, reaching a value of 4.1 μF/cm2. Capacitance-voltage (C-V) measurements revealed that, following a two-cycle chemical treatment, frequency dispersion at accumulation regime and flat-band voltage shift disappeared in the case of the 1.3 μm SiNWs, which is indicative of effective removal of structural defects at the SiNW surface. In the case of the 2.4 μm SiNWs, frequency dispersion at accumulation persisted even after the two-step chemical treatment. This is attributed to a porous Si layer at the SiNW tops, which is not effectively removed by the chemical treatment. The electrical losses of MIS capacitors in both cases of SiNW lengths were studied and will be discussed. [ABSTRACT FROM AUTHOR]

In this work ultrathin strained silicon layers grown on relaxed Si0.9Ge0.1 substrates were oxidized under high thermal budget conditions in N2O ambient at 800 °C. The results indicate that the density of interface traps depends on the extent of the oxidation process. If the strained Si layer is totally consumed the density of interface traps reduces to almost half the value as compared to the case where a part of the strained Si layer still remains. The results indicate that the two existing interfaces of the strained Si layer, the SiO2/strained-Si and the strained-Si/Si0.9Ge0.1, contribute in parallel to the measured interface trap density. In addition, the buried strained-Si/Si0.9Ge0.1 interface constitutes a major source of the observed high density of interface traps. [ABSTRACT FROM AUTHOR]

Dielectric impedance measurements as well as transient current–voltage (I–V) characteristics under conditions of forward and reverse bias are reported in aluminum/porous silicon (PS)/p-cSi structures at different temperatures. Under reverse bias conditions, the electrical conduction of the structures can be modeled by a simple equivalent circuit of two parallel RC networks in series combination, representing a bulk and a junction region. The bulk conduction is ohmic. From the detailed analysis of the PS/cSi junction, the carrier concentration NA and the depletion layer width W are evaluated at each temperature. The elapsed time t0 from the onset of the square pulse, at which the transition from the dominant bulk resistance to junction conduction takes place, is a function of temperature. As the temperature decreases, conduction due to bulk resistance dominates over junction conduction. On the other, hand forward conduction is dominated from the bulk. Two conduction mechanisms are present. As the time proceeds, Poole–Frenkel conduction follows an ohmic conduction. The time after the onset of the square voltage pulse, at which this turnover takes place, is a function of temperature. [ABSTRACT FROM AUTHOR]

The electrical behaviour of Al/Al2O3/p-Ge MOS capacitors, with 10 nm oxide thickness, has been studied in the temperature range between 130 K and 330 K. The ALD method for the Al2O3 deposition has been used. C-V and G-f measurements reveal high values of the density of interfacial traps Dit, suggesting the presence of leakage currents. Conductivity mechanisms for the leakage currents have been studied, on the basis of J-V characteristics of the structure as a function of temperature. In the measured voltage region (0-2.5 V), tunneling is proposed as the dominant mechanism. Specifically, as the applied field increases, Fowler-Nordheim mechanism gradually contributes to the, observed at low fields, Ohmic conduction (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The lipophilic cationic radiotracer 99mTc-sestamibi, known to be concentrated within mitochondria, is widely used for myocardial perfusion and to a lesser extent for muscle metabolism imaging. However, the exact distribution pattern in skeletal muscle has not been yet studied in detail. The present study aims to investigate the 99mTc-sestamibi uptake in rat skeletal muscle and myocardium in relation to their metabolic characteristics. 99mTcsestamibi was i.v. administered in twenty adult male Wistar rats and uptake, as percent of injected dose per tissue gram (%ID/g), in the myocardium, soleus, extensor digitorum longus and gastrocnemius muscles was assessed 2 h after the injection. Muscle uptake was also correlated with myocardial uptake, muscle weight and body weight. Skeletal muscle 99mTc-sestamibi uptake was a small (9-16 %) fraction of that found in myocardium (1.71±0.63 %ID/g). Among the three hindlimb muscles considered, the slow-oxidative soleus muscle showed the highest uptake (0.28±0.16 %ID/g). Metabolically diverse parts of the gastrocnemius muscle showed different uptake. Skeletal muscle uptake was positively correlated with myocardial uptake and both were negatively correlated with tissue and body weight. Skeletal muscle and myocardium 99mTc-sestamibi uptake is related to their metabolic profile. Myocardium, with an exceptional rich mitochondrial concentration, shows much higher 99mTc-sestamibi uptake compared to skeletal muscles. Among muscles, uptake is dependent on their mitochondrial content. Evidence of matching exists between myocardial and muscle uptake, and both are size-dependent. [ABSTRACT FROM AUTHOR]

Aim: The effect of long-term endurance training on skeletal muscle and myocardial uptake of 99mTc-sestamibi, a radiopharmaceutical accumulating in the mitochondria, was investigated. Methods: Twenty-six Wistar rats were divided into a trained (5 days week−1 endurance running for 14 weeks) and an untrained group. On completion of training, 99mTc-sestamibi was administered and, 2 h post-injection, the myocardium and the soleus, extensor digitorum longus (EDL) and medial gastrocnemius (MG) muscles were removed for the measurement of cytochrome c oxidase (CCO) activity and 99mTc-sestamibi uptake. Tissue 99mTc-sestamibi kinetics was preliminarily studied in 16 other rats for up to 2 h post-injection. Results: Two hours post-injection 99mTc-sestamibi uptake was either stable (myocardium) or still rising (skeletal muscles). Both CCO activity and 99mTc-sestamibi uptake decreased in the same order (myocardium, soleus, EDL, MG) in the tissues examined. The CCO activity of the EDL and MG muscles was higher ( P < 0.05) in the trained compared to the untrained group. 99mTc-sestamibi uptake in the soleus and EDL muscles was higher ( P < 0.05) in the trained compared to the untrained rats, whereas the difference in MG was marginally significant ( P = 0.06) in favour of the trained group. Conclusions: Long-term endurance training, resulting in elevated skeletal muscle CCO activity, is also associated with a similar increase in 99mTc-sestamibi uptake. This finding suggests that 99mTc-sestamibi could be used in imaging assessment of skeletal muscle metabolism with possible applications in both clinical and sports medicine settings. [ABSTRACT FROM AUTHOR]

Brown adipose tissue (BAT) physiology and imaging have recently attracted considerable attention. BAT is characterized both by enhanced perfusion and increased mitochondrial activity. 99mTc-sestamibi is a lipophilic cationic tracer that concentrates in mitochondria. Data on the accumulation of 99mTc-sestamibi in BAT are currently lacking. This study investigates the in vivo 99mTc-sestamibi uptake in rat BAT. 99mTc-sestamibi was administered in male Wistar rats of various age and body size. 99mTc-sestamibi uptake was measured in vitro in BAT and white fat (WF) together with cytochrome c oxidase activity. Both 99mTc-sestamibi uptake and cytochrome c oxidase activity were higher in BAT than in WF (P<0.05). 99mTc-Sestamibi uptake in both BAT and WF was negatively related to body weight (r = -0.96 and -0.89, respectively) as was the BAT/WF uptake ratio (r = -0.85). These data show a higher 99mTc-sestamibi uptake in BAT compared to WF, in agreement with the high mitochondrial content and respiratory activity of the former. The strong negative correlation between 99mTc-sestamibi uptake in BAT and body weight (negative allometry), is in accordance to increased needs of thermogenesis in smaller animals. Implications of increased 99mTc-sestamibi uptake in BAT in radionuclide imaging are also discussed. [ABSTRACT FROM AUTHOR]